Analyzes of peptide hormones by ion spray mass spectrometry coupled with high-pressure liquid chromatography have been studied for the simultaneous quantitations of insulin and it's related biologically active peptide hormones ; glucagon, secretin, beta-endorphin, somatostatin, angiotensin I, II, and III, gastrin releasing peptide, atriuretic peptide, adrenocorticotropic hormone, gastric inhibitory polypeptide, and vasoactive intestinal polypeptide. Selected ion monitoring (SIM) was made at the base peaks of the corresponding analytes. All peaks were separated within 35 min. The simultaneous LC/MS of each component of the mixture of 13 peptides gave calibrationcurves with satisfactory linearity over the concentration range of 14 fmol/ mu 1 to 6 pmol/ mu 1.Attempts were also made to obtain higher sensitivity by the use of mitrix-assisted laser desorption (MALD) ionization coupled with time of flight (TOF) mass spectrometer and obtained the sensitivity of 5 fmol.Further investigations for the quantitation of peptide hormones in blood are in progress.